The field of the disclosure relates generally to rotary machines, and more particularly, to a blade with shank features that facilitate reducing stress peaks and gradients within the shank.
At least some known rotary machines include a compressor, a combustor coupled downstream from the compressor, a turbine coupled downstream from the combustor, and a rotor shaft rotatably coupled between the compressor and the turbine. Some known turbines include at least one rotor disk coupled to the rotor shaft, and a plurality of circumferentially-spaced turbine blades that extend outward from each rotor disk to define a stage of the turbine. Each turbine blade includes an airfoil that extends radially outward from a platform towards a turbine casing.
At least some known turbine blades include a shank and dovetail radially inward of the platform to facilitate coupling the blade to the rotor disk. In some cases, an angel wing extends laterally outward from the shank towards an adjacent structure within the turbine assembly. An operational life cycle of at least some turbine blades is limited by fatigue as a result of a mean stress field and a vibratory stress field converging to form a stress concentration in an interface between the blade dovetail and the blade shank.
At least some known turbine blades designs are modified to reduce material in certain portions of the dovetail to relieve stresses in the shank-to-dovetail interface. However, at least some known modifications to the dovetail design require complementary modifications to the rotor disk as well. Additionally or alternatively, an effectiveness of at least some known dovetail modifications in reducing stresses in the shank-to-dovetail interface is limited.